1. Field of the Invention
The present invention relates to a feed controller in an image forming apparatus such as a copying machine or a recording machine for detecting the simultaneous feeding of two or more sheets (hereinafter referred to as multi-feed) to control the operation of the image forming apparatus.
2. Description of the Prior Art
A copying machine or a facsimile machine usually has a mechanism for separating and feeding sheets stacked in a cassette or deck one by one in order to feed the sheets into an image forming station of the machine one by one, form images thereon, and eject the sheets from the machine. However, if for some reason the sheets are not separated one by one, and two or more sheets are fed simultaneously in the machine, there is a high possibility of jam, or even if jam does not occur, leading edges of the piled sheets are staggered from each other so that the image is not formed in a predetermined area of the sheet resulting in waste of sheets.
In the past, in order to detect the double feed, it has been proposed to detect a change in the thickness of the sheet or detect a change in a transmitted light in order to detect the presence or absence of the double feed. However, these methods do not successfully deal with various types of sheets and are technically difficult to attain.